Blackbox JTAG Reverse Engineering
Felix Domke · 2009
JTAG’s IEEE 1149.1 standard is a well-known method to access on-chip scan chains for testmode functionality. But a large part of the accessible test-modes are usually not documented. It will be shown that often these testmodes can be reverse-engineered by looking at the JTAG inputs and outputs. Undocumented test-modes can be pretty powerful tools in gaining “back door ” access to a system. 1